Chuck key safety switch mechanism



July 19, 1955 E. G. MILLER 2,713,407

cnucx KEY SAFETY SWITCH MECHANISM Filed March 13, 1955 POWER SOURCE IN V EN TOR.

EDW/N G. MILLER BY Z ATTORNEY United States Patent CHUCK KEY SAFETY SWITCH MECHANISM Edwin G. Miller, San Diego, Calif.

Application March 13, 1953, Serial No. 342,301

7 Claims. (Cl. 192-129) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes Without the payment of any royalties thereon or therefor.

This invention relates generally to safety switch mechanisms and more specifically to a chuck key safety switch mechanism.

It is an object of this invention to provide a safety mechanism for use in conjunction with chuck keys, which are used to secure drills, metal stock and the like in machine chucks.

It is a further object to provide a mechanism which will prohibit the starting or operation of a machine while the adjustment key is in adjusting position.

It is still a further object to provide a mechanism which will automatically cut off the power to a machine upon the machine adjustment key being removed from its normal position of rest.

Still another object is the provision of a safety device for use in conjunction with machine adjustment keys which does not rely upon the particular construction or configuration of the key for its operation.

Still a further object is to provide a safety device as aforedescribed which automatically returns the key to a position of rest upon removal from the machine and following release by the operator and wherein the device further operates to close a switch in the operating circuit for the machine as the key moves into the position of rest whereby the operator, upon release of the key, may apply his undivided attention to the normal operation of the machine, this in itself constituting a safety feature.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is a partially sectionalized side view of a physical embodiment of the invention.

Fig. 2 is a view in perspective of a drill press utilizing the embodiment shown in Fig. 1.

Fig. 3 is a schematic representation of the electrical circuit used in the embodiment shown in Figs. 1 and 2.

Referring to the drawings, there is provided a chuck adjusting key 11 which may be of known or desired design, and which in its normal resting position is held closely adjacent to a switch mechanism having a housing 12. The key 11 is secured to one end of a flexible line or chain 13, the other end of which is attached to a spring driven reel 14. Spring 15 normally biases reel 14 in a direction to cause the line 13 to be wound about the spool 16 of reel 14, the reel thus normally holding and supporting the key 11 in close adjacency to the housing 12.

Also mounted in housing 12 is a switch 17 which is connected in the power circuit for the drive motor 18 of the machine, such as a drill press 41, as shown, for example, in Fig. 2.

As will be seen from Fig. 3, opening of switch 17 will prohibit energization of the motor, or if the motor is running it will deenergize the motor. In the embodiment shown the switch 17 is in series with the hand and foot switches, 21 and 22 respectively, normally used with the drill press 41.

Switch 17 is mounted in spaced relation from the reel 14 and has a spring actuating arm 19 mounted on and extending from the body 30 thereof. Operatively connected between this arm 19 and a normally open selfbiased spring contact 23 is a reciprocable plunger 25 which is actuated by arm 19 to close switch contact 23 and complementary contact 24, or to allow these contacts to open, depending on whether the arm 19 is being biased toward or away from the body 30 of the switch. Actuating arm 19 is of spring material and is normally selfbiased away from the switch body 30, which thus results in the switch contacts 23 and 24 being normally open in the absence of an external force to bias arm 19 toward body 30, in which latter case the contacts would be closed.

The closing and opening of switch 17 is controlled by an interaction and cooperation between the switch and the reel, line, key (14, 13, 11) combination described above. The line 13 passes through an aperture 31 in the arm 19 which extends into the path of the line from reel 14 to an opening 32 in housing 12 through which the line passes. Near the end of the line to which is secured the key 11 there is provided a bead 33, or other enlargement, which is of larger size than the diameter of the aperture 31 and of smaller size than opening 32. It will thus be apparent that when the line is wound up on the reel the bead 33 will not pass through the aperture 31 and the spring force of the reel will be transmitted through the line 13 and bead 33 to the arm 19 which will close the switch contacts 23 and 24.

Thus, in brief, when the key 11 is in its normal resting position of suspension adjacent the housing 12, the switch 17 is closed. It will be apparent that upon the key being pulled only a short distance from its normal resting position the switch 17 automatically opens.

In operation, the operator pulls the key 11 from its normal resting position in order to adjust the chuck of the machine, or other place to be adjusted as the case may be, and the switch 17 automatically opens since the control arm 19 is released from the pressure normally exerted thereon by the bead 33. The switch will remain open until the key 11 is returned to its normal resting position, thus assuring that the machine cannot be started while the key is engaged in its adjusting location. The return of the key to its normal resting position may be accomplished either by guiding the key to such position by hand or by releasing the key and allowing it to return automatically through the action of the spring-loaded reel 14. Upon such return of the key to this position the switch 17 is automatically closed through the action of bead 33 and control arm 19, thereby readying the power circuit to be energized at the operators will as he desires.

It will thus be seen that this device is simple of operation and requires no extra thought or actions on the operators part to bring it into operation. This is of utmost importance in safety devices. Moreover, the operator need not be at all pre-occupied with the return of the key to its resting place and resultant closing of the power circuit thereby, this all being automatic upon release of the key by the operator, and the operator is thus free to give his undivided attention to the normal operation of the machine by manipulation of either or both of the hand and foot switches 21 and 22. For example, in the event that either of these switches are closed when switch 17 becomes closed, thereby energizing motor 18, the operator being at the operators station for normal operation of the machine, may readily actuate the hand or foot switch, as the case may be, to stop the motor if this is desired, thus avoiding the possibility, as in the use of certain prior art devices, of the operators clothing becoming caught in the rotating machine while he is preoccupied in closing 'the circuit by insertion of the key in a switch device conforming to the configuration of the key.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

,Wh a't is claimed is:

1. A safety mechanism for a machine having a driven part, an adjustment 'key separate from said driven part for adjusting said driven part, a drive motor and a source of power connected to said motor, said mechanism comprising aspring driven reel, a length of flexible line secured at one end to said reel and having said adjustment key secured'at its opposite end, said reel being mounted at a'spaced distance from said driven part, said line normally being urged yieldably into wound relation on the reel by the spring drive thereof whereby said key is mounted in a position adjacent the reel, a switch operable to make and break connection between said source of power and said motor, means on said line for operating said switch in response to movement of said adjustment key whereby said switch is open at all times when said key is moved from said position adjacent the reel into adjusting position onsaid driven part and is closed when said key is released and moved by said reel into close adjacency to said reel.

2. A safety mechanism as in claim 1 wherein said switch has a spring biased control arm extending therefrom and normally biased to open position, said control arm having an aperture therein through which passes said flexible line, said line having an enlargement thereon of larger size than said aperture, said enlargement being between said arm and said key, whereby said control arm is biased to closed position through the coaction of said spring driven reel, said flexible material and said enlargement on said material.

'3. In combination, a machine having a motor, means 'for connecting a source of power to said motor, an adjustable part driven by said motor, an adjusting member separate from said adjustable part for adjusting said part,

biasing means spaced from said adjustable part, and biasing said adjusting member away from said adjustable part, and means controlled by the position of said adjusting member operable to make and break connection between ing said adjusting member away from said adjustable part, and means controlled by the position of said adjusting member relative to said biasing means and said adjustable means operable to make and break connection between said motor and said source of power.

5. The combination as defined in claim 4 wherein there is provided a further manually operable means separate from and in series with said last-named means for making and breaking connection between said motor and a source of power.

6. In a safety system, the combination of a machine having a motor and an adjustable part driven thereby, a power circuit for the motor, separable means manipulatable by the machine operator for adjusting said part, support means providing a normal position of rest for said adjusting means and including a normally open switch in said pow, circuit, an operator control switch in said power circuit in series with said first named switch, means for returning said adjusting means to said position of rest when released by the operator following adjustment of said part thereby, and means associated with said returning means for closing said first named switch as the adjusting means moves to said position of rest.

7. In a safety switch for drill presses and the like machines, a housing mounted on said drill press and having an opening therein, a normally open button actuable switch mounted within said housing, a reel mounted in said housing, a key for said drill press, a long flexible line attached at one end to said reel and extended through said housing opening and having said key attached to the other end thereof, spring means for rotatably urging the reel to wind said line thereon, a spring biased control arm engaged by the button of said switch and extended to said line adjacent said reel, said control arm being biased to normally permit switch opening movement of said button, said arm having an openin therein for passage of said line therethrough, and a bead secured to said line and interposed between said arm and said housing, said bead being larger than said opening in the arm and smaller than said opening in the housing whereby the bead biases said arm to actuate the button to switch closing position when said line is wound on the reel and the bead passes through said housing opening to permit opening of the switch when the key is pulled to withdraw said line from the reel.

References {lite-:1 in the file of this patent UNITED STATES PATENTS 1,691,400 Mitchell Nov. 13, 1928 1,910,217 Hacliield May 23, 1933 2,578,317 Pealer Dec. 11, 1951 2,588,565 Pealer Mar. 11, 1952 2,597,969 Barton May 27, 1952 

